The present invention is directed to a method and apparatus for casting metals around an article having a bore extending along a central axis and defined at least in part by an interior cylindrical wall portion. The invention utilizes a mandrel having a cylindrical exterior surface portion sized to be slidingly positioned in the bore in close relationship with the interior cylindrical wall portion. The mandrel has an annular groove in which is positioned a canted coil spring with a series of outer contact points extending radially outwardly beyond the cylindrical exterior surface portion. The article is moved onto the mandrel to compress the spring and deflect the outer contact points such that the spring imparts an outwardly directed force to the article interior cylindrical wall portion to provide frictional resistance between the spring outer contact points and the interior cylindrical wall portion to retain the article on the mandrel while casting molten metal around the mandrel supported article to form a cast part. The present invention can be used with a variety of types of casting including sand casting, permanent mold casting, low pressure casting and die casting. It is, for example, suitable for die casting an engine block having a separately formed liner cast therein and a mandrel for use in die casting having means for holding a liner thereon and to a dowel for holding a mandrel thereon. The invention is particularly well-suited for use when the mandrel and dowel are disposed in a vertical position or a position approaching vertical during the die casting operation.
In die casting aluminum engine blocks, steel liners for the cylinder bores are positioned around the mandrels during the casting operation so that upon completion of the casting operation, the steel liners become an integral part of the cast engine block. The liners are cylindrical sleeves with a smooth cylindrical interior surface within which the piston moves during operation of the engine. During the die casting operation, the liners are retained on and snugly engage the cylindrical exterior surface of the mandrels. Cylinder liners can be made of steel, cast iron, powdered metal or any material suitable for engine block manufacture. When the mandrels are maintained in a vertical position or a position approaching vertical, it is necessary to provide a holder for retaining the sleeve on the mandrel. The holder for retaining the sleeve must not impede the flow of molten aluminum into the molding cavity or otherwise interfere with the die casting operation. Additionally, upon completion of the die casting operation, the holder must permit the mandrel to be easily withdrawn from the liner without damaging it or the newly cast part.
Similarly, the mandrel is supported on a dowel and means must be provided for retaining the mandrel on the dowel particularly when they are maintained in a vertical position or a position approaching vertical.